This invention relates to a lightweight high strength honeycomb sandwich structure and more particularly, to a multi-layer sandwich material for use as a thermal barrier in space reentry vehicles or the like, as a base for lightweight precision laser mirrors and various other thermal barrier applications.
Prior art thermal barrier material used in spacecraft and the like consists of ceramic or a graphite composite material, both of which are extremely fragile and easily broken. Generally, due to the curvilinear contours of the space vehicles, the barrier material generally takes the form of rectangular tiles. These tiles allow for the curvature of their attachment surface and allow for repairs or replacement of individual sections when localized damage occurs. It has been found that during testing, handling, etc., these tiles are continually being broken and require to be replaced. When replacing broken tiles, generally, additional tiles are broken in the process, thus increasing the cost of repairs and length of downtime of the vehicles.
Prior art high intensity mirror bases, such as those used with lasers, are generally constructed of thick metal, such as copper, so as to prevent any surface variations during changes in structure temperature. These copper structures have many disadvantages. The principal disadvantage is excessive weight, especially in areas of use where weight is a premium, such as in aircraft, space vehicles, etc. This excess weight causes considerable wasted energy when the mirror is carried into space, and in addition, when rotatively operated as a directional mirror, the rotation must be provided at a very slow speed because of the mass and the possible overshoot of the mirror and recorrection requirements.
There has not been an entirely satisfactory lightweight high strength material for use as thermal barrier or laser mirrors, especially in spacecraft, until emergence of the instant invention.